Directional radio receiver



April 15, 1941. H. E. PAUL 2,238,129

DIRECTIONAL RADIO RECEIVER Filed June 25, 1937 v llll- BY fr ATTORNEY Patented Apr. 15, 1941 UNiTED STT nIaEc'rroNAL RADIO RECEIVER Hans Erich Paul, Berlin, Germany, assgnor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporation of Germany Application June 25, 1937, Serial No. 150,267

3 Claims.

other at an angle of 90 degrees and the two an-l tennae being made rotatable about their axis o-f symmetry. In order to produce Vindications in that manner, it has been found necessary to employ considerable power and more or less complicated equipment. If the received energy happens to be modulated at the transmitter, there is an added complication in obtaining synchronism of rotation of the directional loops.

It is an object of my invention to provide a directional radio receiving system wherein the antennae are maintained stationary and where modulations of the received energy are applied at the point of reception rather than at the transmitter.

It is a further object of my invention to provide a directional radio receiver in which locally applied low frequency modulations are caused to deflect the beam of electrons in a cathode ray tube thereby to give an indication of direction of high frequency energy collected by a plurality of dilferently oriented directional antennae.

Further objects and advantages of my invention will be made apparent by the following cletailed description when read in view of the accompanying drawing in which Figure 1 shows diagrammatically a circuit arrangement suitable for use in carrying out my invention, and

Figs. 2 and 3 show respectively different paths that may be traced by the spot on the fluorescent screen of a cathode ray tube, the deflecting circuits of which are jointly controlled by the received high frequency energy and by a local source of low frequency energy.

Referring first to Fig. 1, I show a pair of crossed directional loop antennae I and 3 having a common connection to the cathodes of a push- 'pull arrangement of electron discharge tubes 5.

These tubes are here shown as hexodes, although tubes of other types may be employed, if desired. The separate circuits of diiferent antennae are Germany May 14, 1936 (Cl. Z50-11) connected to the grids I and 9 respectively of the tubes 5. The grids II and I3 are connected respectively to transformer windings I2 and M. A

,l low frequency generator I B supplies modulating rents in the primaries I and Il. 10'

potentials directly to the transformer primary I5 and through a phase shifter IB to the trans-l former primary I'l. A phase difference of 9i) degrees is preferably maintained between the cur- The tubes '5 are jointly controlled by the high frequency and modulating frequency potentials. Thus, it is possible to determine the angle of incidence of the incoming waves.

A receiving amplifier and rectifier is shown having an input circuit connected between the common cathode lead of the tubes 5 and a common anode lead to said tubes. A blocking condenser 2I is provided for avoiding the impress of the high anode potential Va upon the grid (not shown) of the first stage in the receiver 2i). The

' output energy from the receiver 20 is fed through pairs of electron discharge tubes 23 and 2Q. The

`to operate as a push-pull arrangement.

3d circuit constituted by a center tapped transformer secondary winding on; the transformers 25 and 28 respectively. 'I'he primaries of these transformers are fed with energy through different circuits, one from the source I6 and the `other from the source I8 of low frequency modulating potentials.

Direct current plate potentials are applied to the anodes of the tubes 23 from a source Va through impedances 2l. The negative side of the source Va is, of course, grounded, as are the cathodes of the tubes 23 and 24.

For indicating the directivity of `the incoming signal, and for indicating the relative response of the different antennae I and 3 to the collected energy, I preferably employ a cathode ray tube 28. This may be of a conventional type in which two sets of capacitive deflecting plates areemployed. One set of plates 29 provides a horizontal deflecting component under control of potentials derived in the push-pull output circuit from the tubes 23, these potentials being impressed upon the condensers 30. The other set of deflecting plates 3| is fed with energy across the condensers 32 from the output circuit of the push-pull tube arrangement 24.

In explanation of the operation of the device as shown in Fig. 1, a few theoretical considerations will now be presented.

Let it be assumed that the direction of the incoming signal forms with the plane of the antenna loop l an angle qi. The potential in the two loops will then be:

A sin asin 21rht and A cos .sin 21rh1;

where h is the frequency of the incoming wave. The two loop potentials are each modulated with an audio-frequency voltage having frequency 11, being of like amplitude, but shifted in phase an angle of 90 degrees. Hence, the modulation potentials are B sin 21rnt and B co's 21rnt The high frequency potentials resulting from modulation are jointly amplified in a standard receiver and rectified. The audio-frequency voltage which is obtained is C cos (21rntia) Where a depnds upon the combination of loopand modulation potentials that has been chosen, but once so chosen is constant for a given arrangement.

If this potential, so far as its phase is concerned, is compared with one of the modulation potentials B cos Zent or B sin 21rnt, then, with suitable arrangements, the angle, i. e., the angle of incidence of the incoming waves, is determinable.

In a quiescent state, that is to say, when no electrical waves are coming in, a circular pattern appears upon the screen of the Braun tube. The size of the circle is a function of the grid potential of the push-pull device. Upon reception of electric waves stationary patterns will generally appear on the screen of the Braun tube as shown in Figs. 2 and 3 with sharp points.

The position of the line of symmetry of the pattern depends directly upon the angle of incidence of the transmitter in relation to the loop arrangement so that, if the loop is suitably positioned in relation to the Braun tube, it will be readily possible to determine the position of the transmitter. Ambiguity of such indication of direction `can be avoided by use of an auxiliary antenna as known in the prior art.

Various modifications of my invention will possibly be suggested by the foregoing description, but they would nevertheless be included in the scope of the invention itself.

I claim:

1. A directional radio receiving system having two differently oriented directional antennae for the collection of high frequency energy, means K are separately fed with energy from one and the for separately modulating the energy collected by each antenna, means for maintaining a phase difference between the modulations of the energies collected by different antennae, an indi-cating device comprising a cathode ray tube having an electron gun for producing a spot on a fluorescent screen, and having horizontal and vertical beam deflecting means for causing the spot to trace a two-dimensional pattern on said screen, and indicating means including separate circuits to said deflecting means, one circuit constituting means operative in dependence upon the strength of the energy collected by one said antenna for controlling the horizontal deflecting means, the other circuit constituting means similarly operative in respect to the energy collected by the other antenna for controlling the vertical deflecting means, whereby the direction from which the high frequency energy is received is caused to be indicated.

2. Direction indicating apparatus comprising two directional antennae, the directional axes of which are normal one to the other, a receiving circuit having two parallel branches each under separate control of signals received by a respective one of said antennae, a two-phase modulating source, means for impressing differently phased low frequency modulations from said source on different branches of said receiving circuit, a cathode ray-tube having two deflecting circuits each under the joint control of an appropriate branch of said receiving circuit and the last said means, and means for causing said cathode ray tube to exhibit a two-dimensional image the pattern of which signifies the direction from which said signals are received.

3. A direction iinding system having a pair of stationary directional lop antennae, a receiving and combining circuit having two electron discharge tubes the two input `circuits of which other antenna respectively, means including a local low frequency oscillation generator and phase differentiating device for applying to said input circuits modulating potentials having a quadrature phase relationship to one another, indicating means comprising a cathode ray tube oscilloscope having control devices including deflecting circuits for producing a stationary pattern on an oscilloscope screen, and means for rendering said control devices separately responsive to the output energies respectively derived from the output circuits of said discharge tubes.

HANS ERICH PAUL. 

